Merge r1762580, r1762701, r1762702, r1762718, r1762723, r1762742, r1762743,...

Merge r1762580, r1762701, r1762702, r1762718, r1762723, r1762742, r1762743, r1774538, r1779354 from trunk:

event: use atomics for *timeout_queue->total since it's updated concurrently,
and move TO_QUEUE_*() macros to functions.


event: add/remove from/to the pollset outside of the critical sections.

We don't need external locking since it's created with APR_POLLSET_THREADSAFE,
hence reduce those sections to the lowest cycles possible.

A spinlock may be interesting instead of the mutex now, we won't block and the
TO_QUEUE_*() and process_timeout_queue() operations are fast...



event: follow up to r1762701: update log tag.

event: avoid unnecessary listener/polling wake ups (context switches) by using
apr_pollset_wakeup(), when implemented, to signal the listener according to the
next timers or timeout queues expiry (updated at insert and maintenance time).



Follow up to r1762718: CHANGES entry.

event: follow up to r1762718.
We still need to kill kept-alive connections in normal/expiry processing if...